21648 is nontrivially palindromic in base 9.
It is a nude number because it is divisible by every one of its digits.
It is a nialpdrome in base 8 and base 15.
It is a zygodrome in base 15.
221648 is an apocalyptic number.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 21648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31248).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21648 is a wasteful number, since it uses less digits than its factorization.
21648 is an odious number, because the sum of its binary digits is odd.
The square root of 21648 is about 147.1325932620. The cubic root of 21648 is about 27.8701470233.
The spelling of 21648 in words is "twenty-one thousand, six hundred forty-eight".